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Thread: Carbon Fiber Leading Edge?

  1. #1

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    Default Carbon Fiber Leading Edge?

    I am at the point where I’ll be fitting the leading edge fiberglass on my STI wings. Is there any reason that they can’t be made out of carbon fiber. They seem like a lot of weight that could be shaved down. Is there a stiffness issue or otherwise preventing the use of carbon fiber?

    Just trying to shave off a bit of weight where practical.

    Thanks

  2. #2
    patrick.hvac's Avatar
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    Default Re: Carbon Fiber Leading Edge?

    The carbon with direct contact on the aluminum spars would be a galvanic corrosion problem wouldn't it?
    🇨🇦CANADA
    Flying | SS7 | G3X | Edge 912

  3. #3
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    Default Re: Carbon Fiber Leading Edge?

    Quote Originally Posted by patrick.hvac View Post
    The carbon with direct contact on the aluminum spars would be a galvanic corrosion problem wouldn't it?
    Galvanic reaction (or corrosion) occurs when two dissimilar metals come in contact with each other.
    Like steel touching aluminum. Add a little humidity / water and the reaction starts.
    Carbon fiber contacting aluminum should be Ok.

    Don't know what Kitfox sells today. When I built my Classic IV, It come with plastic leading edges that I had to glue on with 3M structural adhesive.
    Completed my Classic 4, May 2003. It had std wings. speedster tail.
    912 UL Rotax. Sold to a person in Spain.

    Completed a Skybolt December 2018

  4. #4
    Senior Member jiott's Avatar
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    Default Re: Carbon Fiber Leading Edge?

    There is a corrosion problem with carbon contacting aluminum; that's why the builder's manual says NOT to mark aluminum with a pencil, use a fine sharpy instead.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  5. #5
    Administrator DesertFox4's Avatar
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    Default Re: Carbon Fiber Leading Edge?

    What Jim said.


    DesertFox4
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  6. #6
    taff's Avatar
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    Default Re: Carbon Fiber Leading Edge?

    This could be of some interest

    https://flightsafety.org/amb/amb_nov-dec89.pdf
    Completed my Classic 4, May 2003. It had std wings. speedster tail.
    912 UL Rotax. Sold to a person in Spain.

    Completed a Skybolt December 2018

  7. #7
    patrick.hvac's Avatar
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    Default Re: Carbon Fiber Leading Edge?

    https://youtu.be/yRpMZaU8zKw
    Dark Aero did a good carbon aluminum corrosion video as well as Mike Patey.

    This is a great application for S-Glass and a good resin I would think.
    🇨🇦CANADA
    Flying | SS7 | G3X | Edge 912

  8. #8
    Senior Member PapuaPilot's Avatar
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    Default Re: Carbon Fiber Leading Edge?

    Quote Originally Posted by taff View Post
    This could be of some interest

    https://flightsafety.org/amb/amb_nov-dec89.pdf
    What part of it? It is a 16 page document with about 40 articles.

    Here is a document from the FAA that covers that topic at hand:
    http://www.tc.faa.gov/its/worldpac/t.../tctn17-42.pdf

    The bottom line is you don't want to use carbon fiber where it touches aluminum, especially to such a critical part of structure like the spar. There are several other ways to save weight.
    Phil Nelson
    A&P-IA, Maintenance Instructor
    KF 5 Outback, Cont. IO-240
    Flying since 2016

  9. #9
    Senior Member jrevens's Avatar
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    Default Re: Carbon Fiber Leading Edge?

    There was a company here in Colorado making a carbon fiber airplane patterned after something like a Swift or maybe a Falco... I don’t remember. It was a vey impressive and sophisticated design. Our EAA chapter had a tour of their factory. It was a first class operation and involved several engineers as I recall. Anyway, the point is that they went to great lengths in the design to keep aluminum and carbon fiber structure conductively separated to prevent corrosion. They even used very expensive special fasteners (titanium?) almost exclusively, as well as special coatings. It was quite a few years ago. The linked article stresses scratching of the aluminum surface by a pencil, but the graphite that can remain on the surface, even microscopically, is definitely also an important issue regardless of any scratching.

    the Kitfox wing is relatively flexible and carbon fiber isn’t. That might or might not be an issue. One of the advantages of making the Laker leading edge out of a thin fiberglass laminate is flexibility. Making it in 2 separate pieces as they do probably helps to accommodate that, as well as thermal expansion and contraction. Of course it makes it easier to ship (& possibly manufacture as well?). The Laker leading edge is so thin that I wonder how much of a weight factor it would be compared to a carbon fiber one.

    The Dark Aero video was very good!
    Last edited by jrevens; 04-15-2021 at 09:19 PM. Reason: Added comment.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
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  10. #10
    taff's Avatar
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    Default Re: Carbon Fiber Leading Edge?

    Quote Originally Posted by PapuaPilot View Post
    What part of it? It is a 16 page document with about 40 articles.

    Here is a document from the FAA that covers that topic at hand:
    http://www.tc.faa.gov/its/worldpac/t.../tctn17-42.pdf

    The bottom line is you don't want to use carbon fiber where it touches aluminum, especially to such a critical part of structure like the spar. There are several other ways to save weight.
    Sorry about that.
    This was my response to Jim (post # 4). He mentioned the pencil not to be used to mark aluminum.
    My focus is not the corrosion but the scoring damage to aluminum that a pencil can cause.
    Of coarse If you score aluminum with fiberglass, the same damage can occur.
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    Completed my Classic 4, May 2003. It had std wings. speedster tail.
    912 UL Rotax. Sold to a person in Spain.

    Completed a Skybolt December 2018

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